Increased expression and mutation of p53 in choroidal melanoma

Germline mutation in the TP53 gene in uveal melanoma

We performed comprehensive molecular analysis of five cases of metastasizing uveal malignant melanoma (UM) (fresh-frozen samples) with an NGS panel of 73 genes. A likely pathogenic germline TP53 mutation c.760A > G (p.I254V) was found in two tumor samples and matched nontumor tissue. In three cases, pathogenic BAP1 mutation was detected together with germline missense variants of uncertain significance in ATM. All cases carried recurrent activating GNAQ or GNA11 mutation. Moreover, we analyzed samples from another 16 patients with primary UM by direct Sanger sequencing focusing only on TP53 coding region. No other germline TP53 mutation was detected in these samples. Germline TP53 mutation, usually associated with Li-Fraumeni syndrome, is a rare event in UM. To the best of our knowledge, only one family with germline TP53 mutation has previously been described. In our study, we detected TP53 mutation in two patients without known family relationship. The identification of germline aberrations in TP53 or BAP1 is important to identify patients with Li-Fraumeni syndrome or BAP1 cancer syndrome, which is also crucial for proper genetic counseling.

Expression of p53 Protein in Pterygium

Purpose

The pathogenesis of pterygium is still not completely understood and many environmental factors, including ultraviolet (UV) radiation, play an important role in its etiology. Chronic exposure to UV radiation causes mutations in the p53 tumor suppressor gene, eventually leading to tumor formation. We analyzed the immunohistochemical expression of p53 proteins in pterygial tissues to determine the role of the p53 tumor suppressor gene in the development of pterygium.

Methods

Pterygial specimens were studied immunohistochemically using antibodies against p53 protein.

Results

Out of 38 specimens studied, 35 (92.1%) had conjunctival epithelial cells without p53 specific nuclear staining. Only three specimens (7.9%) had a few p53 stained cells. The role of UV radiation in the pathogenesis of pterygium is supported by epidemiological, geographical and microscopic findings. However, our results are not consistent with these data on a genetic basis.

Conclusions

We conclude that defective p53 tumor suppressor gene function seems to have no role in the pathogenesis of pterygium.

Simvastatin induces caspase-dependent apoptosis and activates P53 in OCM-1 cells

Simvastatin is a cholesterol-lowering drug which exhibits numerous pleiotropic effects including anti-cancer activity. Yet, the anti-cancer effects in choroidal melanoma remain poorly characterized. Therefore, in this study, we investigated the effects of simvastatin on OCM-1 cells growth, apoptosis and cycle. Simvastatin showed an inhibitory effects on OCM-1 cells viability in dose-dependent (2-10 μM) and time-dependent (24-72 h) manner. Further study suggested that simvastatin-induced inhibition OCM-1 cells proliferation was associated with G1 phase arrest, decreased protein and mRNA expression of proliferation marker cyclin D1, cyclin E, cyclin dependent kinase (CDK)2 and increased expression of CDK inhibitory protein P21. In addition, simvastatin resulted in an increase in levels of reactive oxygen species (ROS) in OCM-1 cells and simvastatin significantly triggered apoptosis in OCM-1 cells, which was characterized by increased chromatin condensation, activation of caspase-9 and cleaved-caspase-3, increased expression mitochondrion-related apoptosis protein of P53, Bax and decreased expression of Bcl2 and iASPP. Collectively, our study demonstrated that simvastatin can efficiently inhibit proliferation and induce apoptosis in OCM-1 cells.

Genetic Study of Familial Uveal Melanoma

PURPOSE

To evaluate a kindred with familial uveal and cutaneous melanoma and to identify potential genetic and environmental factors that may predispose individuals to develop uveal melanoma.

DESIGN

Family-based case report with detailed clinical and genetic evaluation.

PARTICIPANTS

Ten siblings in a single nuclear family.

METHODS

Evaluation of a large sibship via family history, complete eye and skin examinations, environmental risk factor questionnaire, and genetic testing, as well as a MEDLINE search of familial uveal melanoma kindreds.

MAIN OUTCOME MEASURES

Cutaneous and ocular nevi, benign and malignant neoplasms of skin and other sites, brief skin cancer risk assessment tool risk classification for cutaneous melanoma, DNA sequencing of p16INK4a and p14ARF genes, and citations on familial uveal melanoma.

RESULTS

The proband and his mother had uveal melanoma, 3 cutaneous melanomas occurred among 2 siblings, and 2 other siblings had basal cell carcinomas. No germline mutations were detected in the melanoma-associated tumor suppressor genes p16INK4a and p14ARF. Seven out of 10 siblings had a history of cutaneous and/or ocular nevi. Of the 3 subjects without nevi, 2 had histories of eye or skin malignancies (1 uveal melanoma, 1 basal cell carcinoma). Three of the 10 siblings had relevant ocular findings (2 choroidal nevi, 1 uveal melanoma). Six were also found to be in the "high-risk" classification for cutaneous malignancies based on scores from a previously validated risk assessment tool. This family, combined with the 91 previously reported familial uveal melanoma kindreds, brings to 92 the total number thus far recorded.

CONCLUSIONS

Our results strengthen the association between uveal melanoma, atypical nevi, and cutaneous melanoma. This relationship supports the recommendation that individuals with a personal or family history of uveal melanoma, particularly in combination with atypical nevi, should be regularly screened for uveal and cutaneous melanoma.

The role of cell cycle regulatory proteins in the pathogenesis of melanoma

The transformation of melanocytes to melanoma cells is characterised by abnormal proliferation resulting from alterations in cell cycle regulatory mechanisms. This occurs through alterations in the two major cell cycle regulatory pathways, the retinoblastoma (Rb) and p53 tumour suppressor pathways. This review summarises the current knowledge of alterations in these two pathways at G1/S transition and specifically the role of the key cell cycle regulatory proteins pRb, p16INK4a (p16), cyclin D1, p27Kip1 (p27), p53 and p21Waf1/Cip1 (p21) in the pathogenesis of melanoma. It also considers their prognostic significance. Current data indicate that alterations of cyclin kinase inhibitor (cdki) levels are implicated in the pathogenesis of melanoma and may be useful prognostic markers. However, large validation studies linked to comprehensive clinical follow up data are necessary to clarify the prognostic significance of cell cycle regulatory proteins in individual patients.

Chromosomal abnormalities, p53 and Bcl-2 expression and clinical outcome in choroidal melanoma

OBJECTIVE

To determine whether alterations of p53, Bcl-2 and chromosomes were present in choroidal melanoma and to further characterize the prognosis of these changes.

METHODS

The expression of p53 and Bcl-2 protein was assessed by immunohistochemistry from paraffin blocks. Tumours were analysed by comparative genomic hybridization (CGH) to identify chromosomal aberrations. Fifteen tumours were studied, and the survival results were compared by Spearman correlation analysis with a mean follow-up of 36.5+/-8 months. The majority of tumours were mixed (eight cases), and the others were spindle cell (four cases) and epithelioid cell (three cases) types. Four patients have already died due to metastatic disease.

RESULTS

p53 was expressed at a low percentage in only two tumours. There were no differences in Bcl-2 expression in our cases. Bcl-2 was expressed by the majority of cells in all cases. Chromosomal copy number aberrations were detected in 10 of the 15 patients by CGH analyses. A gain at chromosome 8 and a loss at chromosome 3 were the most frequently seen abnormalities. The other aberrations observed were losses at 6q, 7q14 and 17p13-15, and gains at 6p and 18q. Two of the three cases with a loss at 17p13 showed a low percentage expression of p53. No relationship was determined between the chromosomal abnormalities, cell type, expression of p53 and survey. The presence of a chromosome 6q deletion in two of the four patients who died of metastatic disease may indicate that chromosome 6q deletion may be correlated with a poor prognosis.

CONCLUSIONS

Our results suggest that choroidal melanomas show high levels of chromosomal alterations. Further studies are necessary to determine the correlation between chromosomal abnormalities and prognosis.

EXPRESSION OF CELL CYCLE RELATED PROTEINS IN A RAPIDLY GROWING UVEAL MALIGNANT MELANOMA

PURPOSE

To report the clinical and immunohistochemical findings of a rapidly growing uveal melanoma.

METHODS

A 71-year-old Japanese woman was diagnosed with a juxtapapillary uveal melanoma by clinical examination. The tumor grew rapidly with a 31.5-day doubling time. An enucleation was performed, and immunohistochemical examination for cell cycle proteins was performed in addition to routine histopathologic examination.

RESULTS

The melanoma cells were classified as spindle B-cells. The tumor cells were positive for HMB-45 protein, but negative for S-100 protein. The tumor showed immunohistochemical staining for p16 and Bcl-2, although p53 was not detected. Immunoreactivity for pRb was found in normal retinal and choroidal cells but not in the tumor cells.

CONCLUSION

This report describes a unique case of rapidly growing uveal melanoma, which showed low histopathologic grade while the cell cycle protein immunohistochemical profile suggests a more aggressive phenotype. The evaluation of cell cycle proteins may be useful adjunctive method to enhance the understanding of uveal melanoma growth patterns.

Molecular genetics of uveal melanoma

In the past decade, there have been impressive advances in our understanding of chromosomal, genetic and molecular alterations that occur in uveal melanoma. Nevertheless, a coherent picture of the molecular pathogenesis of this eye cancer is yet to emerge. Herein, we review the findings to date, discuss the insights they provide, and suggest future directions for molecular research in uveal melanoma.

Treatment of pediatric ocular melanoma with high-dose interleukin-2 and thalidomide

Uveal melanoma is the most common primary ocular malignancy, although it is rare in children, and patients presenting with metastatic disease have a median survival of only 2 to 5 months. The tumor is generally unresponsive to systemic chemotherapy, but immunotherapy may be effective in selected patients. This report describes an 8-year-old girl with metastatic uveal melanoma treated with high-dose, bolus interleukin-2 (IL-2) and the antiangiogenic agent thalidomide. She tolerated treatment well and initially responded with stable disease in the liver and pancreas for 23 months. New pulmonary metastases developed and she was re-treated with high-dose IL-2, resulting in regression of her liver lesions and stable pulmonary disease for more than 18 months. These results suggest that IL-2 at high doses, and in combination with thalidomide, may be useful for uveal melanoma with tolerable side effects in children. Further study of this combination in children with immune-responsive tumors is warranted.

Altered expression of Rb and p53 in uveal melanomas following plaque radiotherapy

PURPOSE

To examine the expression of proteins in the Rb and p53 tumor suppressor pathways in uveal melanomas following plaque radiotherapy.

METHODS

Immunohistochemistry and cell culture studies. Immunohistochemistry for Rb, p16, cyclin D1, p53, HDM2, and Bcl-2 was performed on twelve eyes containing posterior uveal melanomas that were enucleated following plaque radiotherapy. Cell culture studies were performed in three cases.

RESULTS

The irradiated eyes were enucleated for radiation complications (five cases), local tumor recurrence (three cases), and other reasons (four cases). On histopathologic examination, all cases showed evidence of tumor cell loss. However, residual tumor cells were present in all cases, including those that were clinically regressed. Residual cells from three of the clinically regressed cases were cultured and demonstrated minimal cell division, marked cell death, and extensive chromosomal damage. Strong p53 staining was observed in six cases (50%) and was significantly associated with recent radiotherapy (P = .04). Abnormal cytoplasmic staining for Rb was observed in four cases (33%).

CONCLUSIONS

Plaque radiotherapy of uveal melanomas induces DNA damage, inhibits cell division, and promotes cell death. These changes may be due, at least in part, to induction of p53, which activates genes involved in both cell cycle arrest and apoptosis. Plaque radiotherapy can also cause alterations in the expression of Rb, but the significance of this finding will require further study.

p53 Immunoreactivity, Ki-67 expression, and microcirculation patterns in melanoma of the iris, ciliary body, and choroid

PURPOSE

The major role of p53 is to modulate cell proliferation, but recently, it has been found that p53 also modulates angiogenesis through several pathways. Because both cellular proliferation and microcirculation patterns are important prognostic markers in uveal melanoma, we tested the relationships between p53 expression, the expression of the cell proliferation marker Ki-67, and the presence of various microcirculation patterns in uveal melanoma.

METHODS

Immunostaining of p53 and Ki-67 using the bp53.12 and the MIB-1 antibodies, respectively, were preformed in 98 uveal melanomas (18 melanomas confined to the iris, 30 ciliary body melanomas, and 50 choroidal melanomas). Percent of p53 positive cells, and the mean MIB-1 positive cell count per high power field were calculated in each section by two observers. Microcirculation patterns were assessed in adjacent PAS stained sections.

RESULTS

p53 immunoreactivity was found in 14 of the 98 melanomas. High proliferative activity and epithelioid cell type were associated with p53 immunoreactivity. However, p53 immunoreactivity was not associated with any of the microcirculation patterns or with tumor location.

CONCLUSIONS

The findings suggest that alterations in p53 expression are associated with the expression of the cellular proliferation marker, Ki-67, but are not associated with the presence of microcirculation patterns.

Prognostic factors in uveal melanoma

Uveal melanoma is the most common primary intraocular malignant tumour, with an annual incidence of approximately six cases per million per year. Approximately 40% of patients with posterior uveal melanoma develop metastatic melanoma to the liver within 10 years after initial diagnosis. Despite high accuracy of diagnosis and availability of various methods of treatment; the mortality due to uveal melanoma has remained unchanged. The prognosis in uveal melanoma depends on clinical, histopathological and cytological factors. Clinical factors that relate to prognosis include location, size, and configuration of the tumour. Uveal melanoma can arise in the iris, the ciliary body or the choroid. Iris melanomas have the best prognosis and ciliary body melanomas have the worst prognosis. Based on retrospective studies, the mortality rates for uveal melanoma for comparable sized tumours treated by enucleation or other globe conserving methods such as radiotherapy appear to be similar. Histopathological factors such as cell type, mitotic activity, microcirculation architecture, tumour-infiltrating lymphocytes and the presence of extrascleral extension are also significant predictors of survival. More recently, cytological factors such as cell proliferation, cytogenic, and molecular genetic prognostic markers have been identified with the hope of detecting high risk cases for adjuvant systemic immune therapy or chemotherapy. At present, the role of these therapeutic methods is not clearly established.

Deregulation of the Rb and p53 pathways in uveal melanoma

Uveal melanoma is the most common primary eye cancer, yet its molecular pathogenesis is poorly understood. In this study, we investigated the immunohistochemical expression of proteins in the Rb and p53 tumor suppressor pathways in 33 uveal melanomas from enucleated eyes. Strong nuclear staining for Rb was present in most tumors. However, a few cases displayed weak nuclear staining and strong cytoplasmic staining (possibly indicating Rb mutation), and this aberrant staining correlated strongly with failed radiotherapy or thermotherapy before enucleation. Staining for cyclin D1 was positive in most tumors and was associated with advanced age and larger tumor size, which are both poor prognostic factors. Generally, immunostaining for p53 was weak (suggesting a lack of p53 mutations), although p53 positivity correlated strongly with staining for phosphorylated Rb, supporting the notion that inappropriate phosphorylation of Rb can induce p53. Strong immunostaining for MDM2, which can functionally block p53 activity, was observed in most tumors and correlated significantly with female sex. Strong cytoplasmic staining was observed for Bcl2, which can inhibit both p53-dependent and -independent apoptosis. We conclude that Rb and p53 are mutated infrequently in uveal melanoma, but their respective pathways may be functionally inactivated.

Cell cycle and melanoma--two different tumours from the same cell type

Melanoma of the uvea of the eye and melanoma of the skin share a common cell of origin, but differ substantially in their behaviour and response to chemotherapy. There is increasing evidence that this is related to differences in their molecular phenotype, particularly in relation to the expression of cell cycle-associated proteins. Since many cytotoxic agents act by damaging DNA, resistance is often associated with intact mechanisms which allow the neoplastic cells to arrest their growth while DNA is repaired, or to resist apoptosis in response to detection of DNA damage. p53 is important to these processes, but mutation appears to be a less common event in uveal melanoma than in skin melanoma, probably due to the lack of UV exposure in the uvea. There are also differences in proliferation-associated proteins such as c-myc and cyclin D1. Overexpression of the former molecule is associated with a poor prognosis in skin melanoma, but is associated with a good prognosis in uveal melanoma, although there is considerable genetic heterogeneity within each type. While prognostic studies may therefore be of little relevance to individual patients, they continue to inform our understanding of tumour biology.

The prognostic value of cyclin D1, p53, and MDM2 protein expression in uveal melanoma

Malignant uveal melanoma is the commonest primary intraocular tumour in adults. It metastasizes frequently and 50% of patients die within 10 years of diagnosis. The expression of cyclin D1, p53, and MDM2 in uveal melanoma and their relationship to metastasis-free 5-year survival was determined, in order to investigate whether these proteins help to distinguish those patients with a favourable prognosis from those with a poorer one. Ninety-six eyes enucleated for uveal melanomas were immunohistochemically analysed for the protein expression of cyclin D1 and related cell-cycle markers, p53 and MDM2. The evaluation of the specimens was undertaken by two independent pathologists without knowledge of the outcome. Statistical analysis of clinical, morphological, and immunohistological features was performed. A 'favourable outcome' was defined as survival of at least 5 years after diagnosis, without metastases (n=57). An 'unfavourable outcome' was defined as death from metastases within the first 5 years after diagnosis of uveal melanoma (n=39). Cyclin D1 positivity (>15% positive tumour cells) as well as p53 positivity (>15% positive tumour cells) was associated with an unfavourable outcome (for cyclin D1: odds ratio=4. 2, 95% confidence interval 1.5-11.8, p=0.006; for p53: odds ratio=3. 2, 95% confidence interval 1.1-9.3, p=0.03). In addition, cyclin D1 positivity was associated with the presence of extraocular extension of the tumour (p=0.01), with the mixed or epithelioid cell type (p=0. 02), and with the tumour cell MIB-1 positivity (p=0.0001). MDM2 immunoreactivity of the tumour cells showed a potential correlation with clinical outcome (odds ratio=2.1, 95% confidence interval 0.8-5. 8, p=0.13). Multiple logistic regression models showed that cyclin D1 positivity is an independent prognostic factor after control for other prognostic markers. The expression of cyclin D1 in uveal melanoma is associated with a more aggressive course and histologically unfavourable disease. This could serve as a further independent prognostic factor in uveal melanoma.

Telomerase expression in uveal melanoma

BACKGROUND/AIMS

Accumulating evidence indicates that telomerase activity is repressed in normal human somatic cells but reactivated in cancers and immortal cells, suggesting that activation of telomerase activity has a role in carcinogenesis and immortalisation. To date, telomerase in uveal melanoma and, whether, it may have a role in the development or progression of these tumours has not been described. The expression patterns and the activity of telomerase were investigated in 14 uveal melanoma and these results were correlated with histological and immunohistological features of these tumours.

METHODS

A modified PCR based telomeric repeat amplification protocol (TRAP) assay was used to demonstrate telomerase activity in 14 uveal melanomas. In addition, in situ hybridisation was used to demonstrate the expression pattern of the telomerase RNA component (hTR) at the single cell level in eight of these globes.

RESULTS

The TRAP assay revealed moderate telomerase activity in all uveal melanomas examined. In situ hybridisation visualised a moderate to high upregulation of hTR in the melanoma cells but not in the admixed reactive cells. There was no correlation among tumour location, cell type, or growth fraction and the amount of telomerase activity. In addition, the cells of the germinative zone of the lens demonstrated a strong hTR expression.

CONCLUSION

Telomerase activity is upregulated in uveal melanomas. The expression of hTR was located to the tumour cells and not the reactive tumour infiltrating cells. Strong telomerase expression was also demonstrated in cells of the germinative zone of the lens.

Tumor suppressor genes in ophthalmology

Tumor suppressor genes have a diversity of functions, but they have in common the property of inhibiting neoplastic transformation. When they become inactivated, a constraint is removed that allows cells to grow inappropriately. Mutations in these genes are now thought to be the initiating events in most cancers. The first tumor suppressor gene was discovered through its role in retinoblastoma, and many other tumor suppressor genes also have important ophthalmic manifestations. The first group of tumor suppressor genes to be discussed are those involved in retinoblastoma and uveal melanoma. These are among the most frequently mutated genes in human cancer and are key regulators of growth and homeostasis. The second group of genes is associated with specific hereditary tumor syndromes with ophthalmic manifestations. These genes function in a variety of molecular pathways and are associated with neoplastic and non-neoplastic abnormalities in restricted tissue distributions. Research on tumor suppressor genes continues to shed light on the molecular pathophysiology of ophthalmic tumors and will increasingly yield diagnostic and therapeutic applications.

c-myc, p53, and Bcl-2 expression and clinical outcome in uveal melanoma

AIMS

Overexpression of c-myc protein has independent prognostic significance in a variety of primary and metastatic cutaneous melanomas which suggests a possible role for this gene in melanomagenesis. We have therefore examined the importance of this oncogene in uveal melanoma and studied the coexpression of two other gene products, Bcl-2 and p53, which might contribute to its effect.

METHODS

The percentage of cells positive for nuclear c-myc expression was estimated by flow cytometric analysis of nuclei extracted from paraffin blocks. The expression of Bcl-2 and p53 protein was assessed by immunohistochemistry. A total of 71 tumours were studied and the results compared with survival with a mean follow up period of 6 years.

RESULTS

c-myc was expressed in > 50% of the cells by 70% of the tumours, and was independently associated with improved survival in a Cox multiple regression-model. Although Bcl-2 was expressed by the majority of the cells in 67% tumours, it was without effect on prognosis. None of the cases studied showed convincing positivity for p53. Analysis of coexpression showed that the best survival was seen in c-myc+/Bcl-2+ tumours and the worst in c-myc-/Bcl-2-tumours.

CONCLUSION

The finding of improved rather than reduced survival in c-myc positive tumours is at variance with skin melanoma. There was no evidence to suggest that c-myc was modulated by upregulation of Bcl-2 or p53 inactivation/mutation. Although Bcl-2 is unlikely to have any effect on tumour growth or metastasis, it could contribute to the general lack of susceptibility to apoptosis in these tumours.

Expression patterns of cyclin D1 and related proteins regulating G1-S phase transition in uveal melanoma and retinoblastoma

BACKGROUND/AIMS

A checkpoint mechanism in late G1, whose regulation via loss of retinoblastoma protein (pRB) or p16, or overexpression of cyclin D1 or cyclin dependent kinase 4 (CDK4), has been proposed to constitute a common pathway to malignancy. The aims of this study were (a) to compare markers of cell cycle G1-S phase transition in an intraocular tumour with known pRB deficiency (retinoblastoma) and compare it with one with an apparently functional pRB (uveal melanoma); (b) to determine if one of these markers may have a role in the pathogenesis of uveal melanoma; and (c) to determine if there is a difference in cell cycle marker expression following treatment of uveal melanoma and retinoblastoma.

METHODS

90 eyes were enucleated from 89 patients for retinoblastoma (n = 24) or for choroidal or ciliary body melanoma (n = 66). Conventional paraffin sections were assessed for cell type and degree of differentiation. Additional slides were investigated applying standard immunohistochemical methods with antibodies specific for cyclin D1 protein, pRB, p53, p21, p16, BCL-2, and MIB-1.

RESULTS

Cyclin D1 protein and pRB were negative in retinoblastoma using the applied antibodies. In contrast, cyclin D1 protein expression was observed in 65% of uveal melanomas; a positive correlation between cyclin D1 cell positivity and tumour cell type, location, growth fraction, as well as with pRB positivity was observed. p53, p21, and p16 could be demonstrated in both tumours. An inverse relation between p53 and p21 expression was demonstrated in most choroidal melanomas and in some retinoblastomas. Apart from a decrease in the growth fractions of the tumours as determined by MIB-1, a significant difference in the expression of G1-S phase transition markers in vital areas of uveal melanoma and retinoblastoma following treatment with radiotherapy and/or chemotherapy was not observed.

CONCLUSION

Retinoblastomas and uveal melanomas, two tumours of differing pRB status, differ also in their immunohistochemical pattern for markers of the G1-S phase transition of the cell cycle. The results of the present study support the concept of (a) an autoregulatory loop between pRB and cyclin D1 in tumours with a functional pRB and the disruption of this loop in the presence of pRB mutation, as well as (b) a checkpoint mechanism in late G1, whose regulation via loss of p16 or pRB, or overexpression of cyclin D1 constitutes a common pathway to malignancy. Further, the results raise the possibility of cyclin D1 overexpression having a role in the pathogenesis of uveal melanoma.

Long term growth arrest of human Tenon's fibroblasts following single applications of beta radiation

AIMS/BACKGROUND

Antimetabolites are increasingly used to manipulate the healing response after filtration surgery, but problems with thin cystic blebs have been encountered with the liquid agents commonly used such as 5-fluorouracil and mitomycin C. beta Radiation appears to be a useful adjuvant treatment for preventing scarring after trabeculectomy, resulting in diffuse rather than cystic bleb formation, but much of the basic cell biology of the ocular fibroblast response to beta radiation remains unclear. The effects of beta radiation on ocular fibroblast proliferation and cell cycling were investigated to determine the nature and duration of these effects on these cells.

METHODS

In vitro cell culture techniques were used to investigate fibroblast proliferation. Cell viability was studied using trypan blue dye exclusion. The effect of radiation on cell cycling was investigated using bromodeoxyuridine uptake. p53 expression was demonstrated using immunocytochemistry.

RESULTS

beta Radiation inhibited fibroblast proliferation in a dose dependent manner. Early cell death was not a prominent feature, but irradiated fibroblasts demonstrated a rapid onset and sustained period of growth arrest. p53 expression was found to be increased in irradiated cells.

CONCLUSIONS

Single doses of beta radiation significantly inhibit Tenon's capsule fibroblast proliferation in vitro over a 28 day period. This inhibition is the result of a rapid onset and sustained period of growth arrest in irradiated cells. Irradiated fibroblasts show an increase in p53 expression, a nuclear phosphoprotein which has been associated with control of the cell cycle. Single applications of beta radiation may be an effective treatment for the prevention of bleb failure as a result of prolonged growth arrest of Tenon's capsule fibroblasts.

Conjunctival melanoma

Conjunctival melanoma is an uncommon tumor that is likely to recur and carries an overall mortality rate of approximately 30%. The seemingly unpredictable and enigmatic character of this entity has initiated much debate over the past decades regarding the etiology, histogenesis, prognosis, and preferred management. This review outlines the historical perspective; incidence and demographics; etiologic factors; histogenesis; cytogenetic findings; clinical characteristics; histopathologic and ultrastructural features; differential diagnoses; classifications; management of primary, recurrent, and systemic disease; survival after conjunctival melanoma; and diverse factors of potential prognostic significance. Finally, a brief outlook on present and future research objectives is provided.

p53 expression in uveal malignant melanomas

Mutation of the p53 gene which is located on chromosome 17p is the single most frequent alteration observed in human cancer. In this study we evaluate malignant melanoma, the most common intraocular neoplasm in adults, for aberrant p53 expression. Twenty enucleation specimens representing one ciliary body and 17 choroidal melanomas and two choroidal nevi were studied by immunohistochemistry utilizing the D07 anti-p53 antibody and the MIB-1 monoclonal antibody. The tumors included two spindle cell and 16 mixed cell (spindle + epithelioid cell) melanomas and two spindle cell nevi. The MIB-1 labelling index ranged from < 1% (two cases), 1-5% (13 cases) and > 5% (five cases). Of the 18 melanomas, 13 cases showed nuclear p53 staining with the p53 index < 1% (two cases), 1-3% (eight cases) and 4-5% (three cases). No p53 staining was observed in two malignant melanomas of the spindle cell type and in two choroidal nevi. In the 13 malignant melanomas of the mixed cell type, there was no correlation between MIB-1 index and p53 immunoreactivity. Immunopositivity was not found in normal choroidal melanocytes. Our study suggests that p53 alterations may be found in uveal melanomas; in our series, p53 positivity was present only in malignant melanomas of the mixed cell type.

Prognostic parameters in uveal melanoma: a review

Histologic cell type, largest tumor diameter and tumor location have traditionally been regarded as the leading predictors of survival for uveal melanoma. Morphological cell typing is, however, subjective to variations in interpretation. More objective classification parameters have emerged from extensive cytomorphometrical and DNA flow cytometrical studies. For patients with uveal melanoma there is no effective therapy if metastases have developed, and the median survival after clinical diagnosis of hepatic metastases is extremely poor. Current research focuses on the mechanisms underlying the metastatic process, including tumor vasculature, cytogenetics, oncogene activation, immunology, melanoma-associated antigens and tumor cell migration (cell-cell and cell-matrix interaction). Several new prognostic parameters have emerged from these studies, such as closed vascular patterns, loss of one chromosome 3, and different indices of cell proliferation. Furthermore, considerable genotypical and phenotypical differences have been found between uveal and cutaneous melanoma. In prospective studies on large series of melanomas a combination of histopathological and/or clinical prognostic parameters might be selected with high sensitivity and specificity, providing a way of selecting patients at high risk of developing metastatic disease, who might be eligible for adjuvant therapy.

Posterior uveal melanoma. The Swedish perspective

Posterior uveal melanoma is the most common primary intraocular malignant tumour and in Sweden some 70-80 new cases present each year. While uveal melanoma is more prevalent in the setting of ocular melanocytosis and neurofibromatosis, there is little conclusive data on the aetiology. Most patients experience a progressive visual field defect and present with a grey or greyish-brown mass of the posterior choroid. Diagnostic procedures include fluorescein angiography, ultrasound and magnetic resonance imaging. In some cases, intraocular biopsy may be required to make a correct diagnosis. Posterior uveal melanomas can usually be managed by any of a number of eye-preserving options like plaque radiotherapy and charged particle irradiation, but eyes containing large tumours are often enucleated. Nearly half of patients with posterior uveal melanoma, and in particular those with large tumours, ultimately succumb to metastatic disease. While most patients with tumour dissemination are treated with systemic chemotherapy possibly combined with interferon, metastatic spread confined to the liver may potentially be managed by intraarterial perfusion chemotherapy or liver resection. However, outcome of patients with systemic disease remains extremely poor with a median survival following detectable tumour dissemination of only two to five months. There are still insufficient data on the impact of various treatments on survival, but a large prospective trial addressing this issue is in progress. The present review summarizes the state-of-the-art knowledge and current management of posterior uveal melanoma from a Swedish perspective.

p53 gene and cell cycling in uveal melanoma

PURPOSE

To determine whether alterations of p53, a tumor suppressor gene, were present in uveal melanoma, and to characterize further the nature of those changes.

METHODS

Immunohistochemical analysis with a monoclonal antibody was used to determine whether alterations of p53 were present in 35 enucleated archival uveal melanomas. Further characterization was done by comparing the p53 gene and cell cycling status by using bromodeoxyuridine staining. The alterations in p53 were characterized using polymerase chain reaction single-strand conformational polymorphism analysis and sequencing.

RESULTS

Four of 35 uveal melanomas showed low levels (0.5% to 5.0%) of positive immunostaining for altered p53 in tumor cell nuclei using monoclonal antibody DO-7. These four tumors had the three highest and the 14th highest bromodeoxyuridine labeling indices, ranging from 1.3% to 7.0%. Polymerase chain reaction single-strand conformational polymorphism analysis of p53 exons 5 to 8 was performed on three p53-positive and six p53-negative tumors, and no altered motility shifts were detected. Sequencing of one of the positive staining specimens confirmed no mutations in exons 5 through 8 in the p53 gene. Double immunohistochemical labeling for both bromodeoxyuridine and p53 in one tumor showed that most of p53-positive cells were in S phase.

CONCLUSIONS

Mutation of p53 is an uncommon event in uveal melanomas. Nuclear accumulation of p53 protein was found in three of the four tumors with the highest levels of cell cycling.

Cell growth and p53 expression in primary acquired melanosis and conjunctival melanoma

AIMS

To evaluate cell growth and the pattern of p53 suppressor gene expression in atypical primary acquired melanosis (PAM) and in recurrent conjunctival melanoma.

METHODS

Eighteen specimens of PAM with atypia and 24 specimens, comprising early and late lesions, from 12 patients with conjunctival melanoma were stained for the proliferating cell nuclear antigen using the PC10 antibody, and for the p53 gene product using the BP53-12-1, 1801 and DO7 clones. The immunoreactive cells were counted manually and the data evaluated statistically.

RESULTS

Seven of nine PAM specimens progressing to melanoma expressed PC10. None of these lesions expressed the p53 gene product. The number of proliferating cells was higher in the late than in the early lesions of conjunctival melanoma. Four of the 12 recurrent melanomas displayed focal, but minimal, p53 expression. The proliferating cell count in the p53 positive tumours was very similar to that of the p53 negative conjunctival melanomas.

CONCLUSION

Examination of the expression of proliferating cells in atypical PAM may be used as an adjunct to predict which lesions will progress to melanoma. The increase in the number of proliferating cells over time in recurrent conjunctival melanomas probably reflects more aggressive behaviour and may be used to monitor recurrence. The absence of p53 expression in PAM and minimal staining of conjunctival melanomas did not correlate with cell growth, suggesting that alterations in the p53 tumour suppressor gene are uncommon and late events in conjunctival melanoma, and that p53 expression is unlikely to be a useful prognostic indicator.

Expression of the p53 protein in malignant melanomas as a prognostic indicator

It is currently widely accepted that the tumour suppressor gene p53 is critically involved in the proliferation and differentiation of tumour cells including melanoma cells. In the present study, we examined 60 cases of primary melanoma to compare the expression of p53 protein with conventional prognostic markers for melanoma such as clinical and histological parameters. No correlation was found between the p53 protein and clinical factors except for the presence of a metastatic node and development to clinical stage II. However, the expression of p53 protein was significantly associated with tumour thickness over 1.5 mm, levels IV and V of invasion, the presence of ulceration, and high mitotic rate for 5-year survival rate. Although many questions still remain to be answered, our results and those of others for various other malignant tumours, implicate p53 in malignant transformation of pigment cells. Indeed, it could be a new marker for an unfavourable prognosis of malignant melanoma, even though the gene mutation in this highly lethal tumour has yet to be established.

TP53 allele loss, mutations and expression in malignant melanoma

p53 alterations at the DNA, mRNA and protein levels were studied in tumour metastases sampled from 30 patients with malignant melanoma. Paraffin-embedded sections from these and an additional 12 patients were examined for the presence of p53 protein. TP53 gene aberrations were found in 7 of 30 (23%) of the patients, six of which showed loss of heterozygosity (LOH). Point mutations were detected in only two cases, one of which had LOH whereas the other was non-informative. Increased levels of p53 mRNA were present in only one tumour with, but in six cases without, detectable DNA abnormalities. Four of the latter and six tumours with normal transcript levels had immunohistochemically detectable levels of p53 protein. In 25 cases in which corresponding primary and metastatic lesions could be compared, closely similar immunoreactivity patterns were observed. Increased expression of the MDM2 gene was found in only one tumour in parallel with overexpression of p53. Altogether, the data indicate that inactivation of the p53 regulatory pathway is not of major significance in the tumorigenesis of malignant melanoma. However, a significant association was found between p53 immunoreactivity and the relapse-free period in patients with superficial spreading melanoma. That increased protein expression was predominantly found in tumours without DNA alterations might suggest a role for the wild-type p53 protein in restricting malignant cell proliferation in these cases.

Immunohistochemical study of p53 protein in human and animal pituitary tumors

In many human cancers, p53 gene mutations are frequently occurring genetic abnormalities, which may be detected by immunohistochemical staining for p53 protein. In the present study, p53 immunoreactivity was investigated in formalin-fixed, paraffin-embedded tissues from human and animal pituitary tumors, using the avidin-biotin-peroxidase complex technique. No p53 was detected in 3 nontumorous human adenohypophyses or in 40 human pituitary tumors including 5 GH cell adenomas, 10 PRL cell adenomas, 2 mixed GH cell-PRL cell adenomas, 2 acidophil stem cell adenomas, 8 ACTH cell adenomas, 1 TSH cell adenoma, 1 FSH/LH cell adenoma, 5 null cell adenomas, 5 oncocytomas, and 1 plurihormonal adenoma. Twenty nontumorous and hyperplastic pituitaries of hGRH transgenic mice and 8 tumors in these transgenic animals were immunonegative for p53. All pituitary tumors found in AVP/SV40 transgenic mice contained p53 immunoreactivity in the nuclei, while the nontumorous adenohypophysis of one such transgenic mouse was negative. It can be concluded that p53 mutations are apparently not involved in the pathogenesis of human pituitary adenomas or of the pituitary tumors which develop in hGRH transgenic mice. However, pituitary tumors in AVP/ SV40 transgenic mice are accompanied by p53 expression.